How to build a quantum-entangled superclock

Combine the extraordinary precision of atomic clocks with the bizarre facets of quantum entanglement, and you get a global quantum network of clocks that does far more than just measure time. Quantum timekeeping could enable startlingly precise measurements of Earth’s terrain.

“You’d be able to see someone digging a tunnel under the U.S.-Mexico border from space,” says Chris Monroe, a physicist at the Joint Quantum Institute at the University of Maryland in College Park.

The technology does not yet exist to build such a superclock, but “all the building blocks are there,” says Harvard physicist Eric Kessler. He and colleagues lay out a blueprint June 15 in Nature Physics.

For more on the mind-blowing implications of linking a new generation of atomic clocks, read SN's Quantum timekeeping feature.